Bump Container Registry to v2.8.0-gitlab

What does this MR do?

Changes the Container Registry version to v2.8.0-gitlab (Changelog)

!3928 (closed) was open previously for the bump to v2.7.8-gitlab, so it should be merged before this one.

Related issues

Related to container-registry#23 (closed)

Checklist

See Definition of done.

• Changelog entry created. Not applicable for Documentation changes and minor changes.
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA, if applicable
• MR targeting master branch
• MR has a green pipeline on GitLab.com
• Equivalent MR/issue for CNG opened if applicable
• trigger-package has a green pipeline running against latest commit

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks